Transgene Pyramiding of theHVA1andmtlDin T3 Maize (Zea maysL.) Plants Confers Drought and Salt Tolerance, along with an Increase in Crop Biomass

Abstract

The pBY520 containing the Hordeum vulgare HVA1 regulated by the rice actin promoter (Act1 5 ) or the JS101 containing the bacterial mannitol-1-phosphate dehydrogenase (mtlD) also regulated by rice Act1 5 and a combination of these two plasmids were transferred into the maize genome, and their stable expressions were confirmed through fourth generations. Plants transcribing a combination of the HVA1+mtlD showed higher leaf relative water content (RWC) and greater plant survival as compared with their single transgene transgenic plants and with their control plants under drought stress. When exposed to various salt concentrations, plants transcribing the HVA1+mtlD showed higher fresh and dry shoot and dry root matter as compared with single transgene transgenic plants and with their control plants. Furthermore, the leaves of plants expressing the mtlD accumulated higher levels of mannitol. Plants expressing the HVA1+mtlD improved plant survival rate under drought stress and enhanced shoot and root biomass under salt stress when compared with single transgene transgenic plants and with their wild-type control plants. The research presented here shows the effectiveness of coexpressing of two heterologous abiotic stress tolerance genes in the maize genome. Future field tests are needed to assure the application of this research.

Transgenic peanut overexpressing mtlD gene confers enhanced salinity stress tolerance via mannitol accumulation and differential antioxidative responses

“…An increase in the mannitol content was recorded in T lines until 2 dS m -1 salinity levels, which decreased thereafter (3 dS m -1 ). Similarly, a wide range of mannitol accumulation (lmol g -1 FW) was reported for other transgenic plants, such as Arabidopsis (0.05-12; Thomas et al 1995), wheat (0.6-2.0; Abebe et al 2003), and maize (0.26-0.56;Nguyen et al 2013). This clearly indicated that even a very low concentration of mannitol can function in maintaining the osmotic adjustments and also improves the osmotic stress tolerance through scavenging of hydroxyl radicals and stabilization of macromolecular structures (Rahnama et al 2011;Bhauso et al 2014a).…”

“…As a strategy for imparting salinity tolerance, overexpressing of mtlD gene coding for MTD has been widely used in various crops (Hema et al 2014;Nguyen et al 2013), including peanut in hydroponic system in our lab (Bhauso et al 2014a). In the present investigation, WT plants exhibited almost negligible, while T lines showed notable MTD activities under salinity stress and non-stress conditions, which suggests the expression of transgene in T lines (Fig.…”

“…At higher salt-content (3 dS m -1 ), T lines MTD1 and MTD4 showed higher accumulation of various sugars including mannitol (Table 1). Similarly, mtlD transgenic maize has also showed comparatively higher accumulation of glucose, fructose, sucrose and inositol under higher salinity conditions (Nguyen et al 2013). Thus, the salinity tolerance might be partially due to the induction of antioxidative machinery, and partially because mtlD transgenes might have exerted a direct regulatory control on metabolism, which could have resulted in protective compounds accumulation either by posttranslational regulation of enzymatic activities or by stabilization of key intermediates, as also reported for herbicide resistance in grass weeds (Cummins et al 2013).…”

“…Among various ways for imparting the salinity tolerance, accumulation of mannitol using E. coli mtlD gene coding for MTD (EC 1.1.1.17), a key mannitol biosynthesis enzyme, has been widely used for the development of transgenic in various crops (Hema et al 2014;Nguyen et al 2013) including peanut (Bhauso et al 2014a, b). Previously, we have reported the successful transfer of mtlD gene in peanut (cv.…”

Transgenic tobacco plants constitutively expressing peanut BTF3 exhibit increased growth and tolerance to abiotic stresses

“…Transcription factors are involved in many cellular processes, and hence, stress responsive transcription factors are considered good candidates for improving stress adaptation. Improvement in stress tolerance by transgenic approaches using transcription factors has been achieved in field crops such as rice (Karaba et al 2007;Yu et al 2013), maize (Nelson et al 2007;Nguyen et al 2013), wheat (Saad et al 2013), soybean ) and potato (Bouaziz et al 2013).…”